Science —

The future of climate change

Nobel Intent takes a look at some of the recent climate change science

There's been quite a lot of climate-related science recently, so I'm going to bundle the most interesting of it together in one post today.

First is a paper in Nature from geologists at Yale and Wesleyan Universities. One difficulty with accurately assessing the potential for increasing CO2 to alter global temperature is that much of the data on climate sensitivity is from the last few thousand years, which makes extrapolation tricky. What's more, the spread of values over that time-frame hasn't been particularly large, up until the beginning of the industrial revolution when we decided to start releasing large amounts of carbon back into the atmosphere.

This new study has used proxy data from geological samples going back 420 million years and compared it to models of climate sensitivity in order to better refine the models. The computer models looked at 10,000 variations in the carbon cycle, such as plants growing faster and sequestering more CO2 in a carbon-rich atmosphere. The advantage of using proxy data going back as far as 420 million years is the inclusion of data from times when the CO2 levels in the atmosphere, and the earth's temperature, were much higher than now. The researchers, Dana Royer, Robert Berner and Jeffery Park, found that weak radiative forcing by CO2, where a doubling of atmospheric CO2 only increases temperature by 1.5?C or less, was highly unlikely. As was the other end of the scale, where doubling of CO2 would cause mean temperature increases of over 5.5?C. Instead, the answer lies in between, which is still far from good news.

The other climate research studies that caught my eye were both featured in PNAS. The first of these concerns the fate of the planet's coral reefs. These enormous living structures are crucial aquatic ecosystems that teem with biodiversity. Sadly, the living coral is highly sensitive to water temperature, which is rising, just like the land. In 2005, the extremely warm sea temperatures that were responsible for the violent hurricanes that devastated the Gulf coast also took their toll on the corals of the Eastern Caribbean, which suffered mass bleaching.

The study, from Simon Donner and colleagues at Princeton, concludes that the warming of the region that lead to the bleaching event in 2005 was most likely due to anthropogenic climate change. In the past, such an event would only happen around once every millennium, but with the rising CO2 levels, if nothing is done it may well happen every two to three decades, unless the corals can adapt to the rising sea temperatures. The paper doesn't address the effects of an increasingly acidifying ocean on coral survival, which may well complicate matters. As CO2 concentration in the atmosphere climbs, more CO2 dissolves forming carbonic acid, which in turn lowers the ocean's pH level making it more acidic. This is obviously bad news for the inhabitants.

The more pessimistic scenario, A2, leads to large local climate change across the globe, with the greatest changes centering on the Southeastern US, Southeast Asia, most of Africa, and South America. Regions around the tropics have the greatest likelihoods of developing novel climates; that is climates not seen on earth before. Unfortunately these regions encompass the greatest densities of biodiversity on the planet.

In the second scenario, B2, mankind gets its act together and works to mitigate change, although the probability of of novel climates arising in the aforementioned areas remain. Those species that can adapt to this fast-changing world will do well; the fate for the others will most likely be the same as the dodo and passenger pigeon.

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